The present invention relates to a system for measuring the tenderness of meat; and more particularly it relates to a system for generating an electrical signal representative of the tenderness of the meat and which is a more reliable and more accurate measure of the tenderness of the meat after it is cooked.
Prior tests for determining the tenderness of raw meat which center upon the use of a probe being inserted into the meat have included the use of both blunt probes pressed into the meat and pointed probes (or needles) which sink into the meat under fixed weight or force. In this latter method, the depth to which the probe descends under the fixed weight is taken to be a measure of the tenderness of the meat. This test (the so-called penetrometer test) has been found not to be entirely reliable and satisfactory.
There is described in the above-identified application a method of measuring the tenderness of meat by inserting a probe with spaced needles into the carcass and measuring the peak penetration resistance force, this measurement being a more reliable and more accurate determination of the tenderness of the meat after cooking, and, hence, a more meaningful measurement.
The present invention relates to an electronic system for use in combination with a probe for measuring penetration resistance force. A force transducer is carried by the probe for generating a signal which is representative of the resistive force incurred during penetration to a predetermined depth. Thus, for a complete penetration stroke, there will be a slightly irregular, but generally increasing signal from the time of initial probe insertion until the probe comes to rest at maximum penetration, at which time the resistive force signal returns to zero.
The embodiment described within is a self-contained, portable unit which is not affected by wide variations in ambient temperature as might, for example, be encountered with a usage at normal room temperature followed by usage in a cold storage area. Thus, a plurality of resistive strain gauges comprise the force transducer, and they are incorporated in an electrical bridge circuit which is energized by storage batteries coupled to the bridge circuit through a regulating network to insure a constant supply voltage for the bridge. The bridge supply voltage and resultant force signal are thus independent of the charge on the batteries and the ambient temperature.
A difference amplifier receives the output signal of the bridge circuit and couples it to a memory circuit. A capacitor in the memory circuit is coupled to the output of the difference amplifier by means of a circuit which permits current to flow unidirectionally into the capacitor thereby generating a charge on the capacitor (and corresponding voltage across the capacitor) which is representative of the instantaneous peak amplitude of the transducer signal. Since the capacitor is not allowed to discharge, the charge stored on the capacitor is indicative of the peak resistive force which occured during the penetration stroke; and the voltage across the capacitor then becomes a measure of the tenderness of the carcass.
A readout circuit generates a visual indication (or permanent record, if desired) of the voltage across the memory capacitor. The capacitor may be discharged by the operator's closing a switch which sets the capacitor charge to a reference level for taking a new measurement.
Provision is also made for charging the storage batteries and for modifying the voltage across the storage batteries under a test load so that the charge may be measured with the same scale of the readout apparatus as is used to read the voltage across the memory capacitor.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing.